Chlorinated vinyl chloride-based resin compositions have been widely used as a material of resin molded bodies, such as building materials. Chlorinated vinyl chloride-based resin compositions are required to have high thermal stability for processing at high temperatures. They need high thermal stability also in order to provide a molded body having thermal stability. Chlorinated vinyl chloride-based resin compositions also need coloring resistance because color is important for resin molded bodies used as building materials. In order to improve such properties as thermal stability and coloring resistance, chlorinated vinyl chloride-based resins are usually mixed with a thermal stabilizer before melt molding.
Conventionally used thermal stabilizers contain a heavy metal such as lead, cadmium, or tin. As concerns have arisen about the toxicity or the adverse effects on the environment of heavy metals, thermal stabilizers or resin molded products free of highly toxic heavy metals, such as lead, have been proposed. For example, Patent Literature 1 discloses a stabilized halogen-containing resin composition that contains a halogen-containing resin and a composite of acid clay and/or activated clay with a calcium hydroxide compound represented by the formula Ca1-x-yM2+xAly(OH)2 (where M2+ is a divalent metal such as Mg, Zn, or Cu; and x and y are respectively within the ranges of 0≦x≦0.4 and 0≦y<0.1).
However, even if a chlorinated vinyl chloride resin is contained with a composite of acid clay and/or activated clay with a calcium hydroxide compound, the stability is insufficient.